500 Minor League Innings = Major League Success?

The old adage stated that 500 minor league  innings was the floor that teams should allow their pitchers to reach before debuting them at the big league level. Doing a rough research session of the past two seasons' ERA qualifiers and their minor league innings, here's what I've established:

1. 152 pitchers qualified for the ERA crown over 2006/2007.
2. Of those 66 had 500 or more minor league innings, and 87 had 450 or more innings.
   
3. 6 of the top 10 ERA leaders qualified for a part of the 87, Roy Oswalt and John Lackey being the top representatives.

On the X axis we see the ERAs from the previous two seasons, on the Y axis we have the amount of minor league innings thrown. There's no clear correlation, but I decided to try one more stat run. My theory was the more more league innings thrown the fewer walks a pitcher would give up.

As it turns out that hunch also has little correlation to support it, despite my previous idea that the longer a pitcher spent in the minors the more refined he could become and the higher to his full potential he'd reach. When I talked about the Rays and James Shields/Andrew Sonnanstine developing better pitches it seems those cases are more isolated than I would've imagine and minor league innings really don't tell us much, instead we should use a pitcher-by-pitcher basis for each situation.